The formation of natural gas is closely related to that of coal and petroleum, as they all originate from organic matter subjected to heat and pressure over millions of years. Natural gas primarily forms from the remains of marine organisms, while coal is mainly derived from plant material, and petroleum is formed from a variety of organic sources, including plants and plankton.
Initially, the organic material accumulates in sedimentary basins where conditions are conducive to preservation, often in anaerobic environments that reduce decomposition. As sediments build up, the organic matter is buried and subjected to increasing temperatures and pressures. This process, known as diagenesis, leads to the transformation of organic material into hydrocarbons.
In the case of coal, this transformation results in the formation of coal seams, primarily from plant material in wetland environments. As pressure continues to increase with deeper burial, the heat and duration of this process can lead to the formation of liquid hydrocarbons, or petroleum, from both plant and animal remains.
As temperature increases further, especially in deeper geological settings, the formation of natural gas is favored. This results from the thermal cracking of larger hydrocarbons into lighter hydrocarbons, such as methane, which is the main component of natural gas.
In summary, while coal, petroleum, and natural gas share a common origin as fossil fuels derived from ancient organic material, their formation processes vary primarily due to the type of organic matter, the depth of burial, and the thermal conditions they undergo over time.